1. Field of the Invention
The present invention relates to novel processes for preparing cyclopentanones of Formula 1,
which are useful for the preparation of benzindene Prostaglandins. The invention also relates to novel cyclopentanones prepared from the processes.
2. Description of the Prior Art
Flolan (Epoprostenol) is the first drug approved by Food and Drug Administration for the treatment of pulmonary hypertension. However, Epoprostenol is extremely unstable and normally has a half-life of about 3˜5 minutes and needs to be administered via continuous intravenous administration and be stored at lower temperatures. Benzindene Prostaglandins, such as UT15 (Treprostinil), are derivatives of Epoprostenol and are a new class of drugs for the treatment of pulmonary hypertension. Benzindene prostaglandins are more stable and thus more convenient and safer in utilization as compared to Epoprostenol.
As shown in Scheme 1, cyclopentanones of Formula 1a are important intermediates for the synthesis of benzindene prostaglandins, such as UT15 (Tetrahedron Letters (1982), 23(20), 2067-70):

However, as shown in Scheme 2, the synthesis of cyclopentanones of Formula 1a should be started with the intermediate B and undergoes eight steps (J. Org. Chem., Vol. 43, No. 11, 1978), and would involve more than 20 chemical steps, including the steps for the synthesis of the intermediate B. Such synthesis is very complicated and only achieves a low yield.

Consequently, there is a demand in the industry for processes for the preparation of cyclopentanones of Formula 1 and benzindene prostaglandins that involve less steps and are more convenient to operate.